UPDATE post-trip:
FWIW, Botin was OK and I'm glad we went and checked the box, but it's nothing to get excited about.
We had a fantastic meal at Casa Juan. Juan himself came to the table and ensured all was great with our evening. Recommended (and a quick, easy 10 minute cab ride from Sol and/or Plaza Major. ^
http://www.asadorcasajuan.es/english...uan-index.html
The Mushroom Bar for a quick tapas was fun but tourisy (it is steps from Botin). I'd go back but wouldn't make a special trip...